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<title>Debugging with GDB: Separate Objdir</title>

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<a name="Separate-Objdir"></a>
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<p>
Next: <a href="Config-Names.html#Config-Names" accesskey="n" rel="next">Config Names</a>, Previous: <a href="Running-Configure.html#Running-Configure" accesskey="p" rel="prev">Running Configure</a>, Up: <a href="Installing-GDB.html#Installing-GDB" accesskey="u" rel="up">Installing GDB</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Compiling-GDB-in-Another-Directory"></a>
<h3 class="section">C.3 Compiling <small>GDB</small> in Another Directory</h3>

<p>If you want to run <small>GDB</small> versions for several host or target machines,
you need a different <code>gdb</code> compiled for each combination of
host and target.  <samp>configure</samp> is designed to make this easy by
allowing you to generate each configuration in a separate subdirectory,
rather than in the source directory.  If your <code>make</code> program
handles the &lsquo;<samp>VPATH</samp>&rsquo; feature (<small>GNU</small> <code>make</code> does), running
<code>make</code> in each of these directories builds the <code>gdb</code>
program specified there.
</p>
<p>To build <code>gdb</code> in a separate directory, run <samp>configure</samp>
with the &lsquo;<samp>--srcdir</samp>&rsquo; option to specify where to find the source.
(You also need to specify a path to find <samp>configure</samp>
itself from your working directory.  If the path to <samp>configure</samp>
would be the same as the argument to &lsquo;<samp>--srcdir</samp>&rsquo;, you can leave out
the &lsquo;<samp>--srcdir</samp>&rsquo; option; it is assumed.)
</p>
<p>For example, with version 7.12.1.20170417-git, you can build <small>GDB</small> in a
separate directory for a Sun 4 like this:
</p>
<div class="smallexample">
<pre class="smallexample">cd gdb-7.12.1.20170417-git
mkdir ../gdb-sun4
cd ../gdb-sun4
../gdb-7.12.1.20170417-git/configure sun4
make
</pre></div>

<p>When <samp>configure</samp> builds a configuration using a remote source
directory, it creates a tree for the binaries with the same structure
(and using the same names) as the tree under the source directory.  In
the example, you&rsquo;d find the Sun 4 library <samp>libiberty.a</samp> in the
directory <samp>gdb-sun4/libiberty</samp>, and <small>GDB</small> itself in
<samp>gdb-sun4/gdb</samp>.
</p>
<p>Make sure that your path to the <samp>configure</samp> script has just one
instance of <samp>gdb</samp> in it.  If your path to <samp>configure</samp> looks
like <samp>../gdb-7.12.1.20170417-git/gdb/configure</samp>, you are configuring only
one subdirectory of <small>GDB</small>, not the whole package.  This leads to
build errors about missing include files such as <samp>bfd/bfd.h</samp>.
</p>
<p>One popular reason to build several <small>GDB</small> configurations in separate
directories is to configure <small>GDB</small> for cross-compiling (where
<small>GDB</small> runs on one machine&mdash;the <em>host</em>&mdash;while debugging
programs that run on another machine&mdash;the <em>target</em>).
You specify a cross-debugging target by
giving the &lsquo;<samp>--target=<var>target</var></samp>&rsquo; option to <samp>configure</samp>.
</p>
<p>When you run <code>make</code> to build a program or library, you must run
it in a configured directory&mdash;whatever directory you were in when you
called <samp>configure</samp> (or one of its subdirectories).
</p>
<p>The <code>Makefile</code> that <samp>configure</samp> generates in each source
directory also runs recursively.  If you type <code>make</code> in a source
directory such as <samp>gdb-7.12.1.20170417-git</samp> (or in a separate configured
directory configured with &lsquo;<samp>--srcdir=<var>dirname</var>/gdb-7.12.1.20170417-git</samp>&rsquo;), you
will build all the required libraries, and then build GDB.
</p>
<p>When you have multiple hosts or targets configured in separate
directories, you can run <code>make</code> on them in parallel (for example,
if they are NFS-mounted on each of the hosts); they will not interfere
with each other.
</p>
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